1. Field
The subject disclosure relates generally to wireless communication and, more particularly, to on-time generation of Zadoff-Chu sequences and computer generated sequences.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, data, and so on. These systems may be multiple-access systems capable of supporting simultaneous communication of multiple terminals with one or more base stations. Multiple-access communication relies on sharing available system resources (e.g., bandwidth and transmit power). Examples of multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Communication between a terminal in a wireless system (e.g., a multiple-access system) and a base station is effected through transmissions over a wireless link comprised of a forward link and a reverse link. Such communication link may be established via a single-input-single-output (SISO), multiple-input-single-output (MISO), or a multiple-input-multiple-output (MIMO) system. A MIMO system consists of transmitter(s) and receiver(s) equipped, respectively, with multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. SISO and MISO systems are particular instances of a MIMO system. A MIMO channel formed by NT transmit and NR receive antennas may be decomposed into NV independent channels, which are also referred to as spatial channels, where NV≦min{NT,NR}. Each of the NV independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput, greater capacity, or improved reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
A Zadoff-Chu sequence is a complex-valued mathematical sequence which, when applied to radio signals, gives rise to an electromagnetic signal of constant amplitude, whereby cyclically shifted versions of the sequence comprising the signal do not cross-correlate with each other when the signal is recovered at the receiver. A generated Zadoff-Chu sequence that has not been shifted is known as a “root sequence”. The sequence then exhibits the useful property that cyclic-shifted versions of itself remain orthogonal to one another, provided, that is, that each cyclic shift, when viewed within the time domain of the signal, is greater than the combined propagation delay and multi-path delay-spread of that signal between the transmitter and receiver. Zadoff-Chu sequence is known as a CAZAC sequence (constant amplitude zero autocorrelation waveform). Zadoff-Chu sequences are used in the 3GPP LTE (Long Term Evolution) air interface in the definition of pilot signals (“reference signals” (RS)), random access preamble (PRACH) and HARQ ACK/NACK responses on Physical Uplink Control Channel (PUCCH).